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Introduction to Aquatic Therapy: Summary
PROPERTIES OF WATER AND PHYSIOLOGICAL EFFECTS
Viscosity Provides resistance to movement in all directions, creating a natural strengthening environment due to friction between liquid molecules. Water provides 12× more resistance than air due to viscosity. Resistance increases with movement speed and surface area. Drag Cumulative effects of turbulence and viscosity acting on an object in motion. As speed increases, resistance to motion will increase. Equipment (kick board) will increase drag and resistance. LEARNING TIP! Refraction A prism effect that occurs when light
Buoyancy Reduces gravitational forces on the body, allowing for earlier intervention in rehabilitation programs. Buoyancy can be assistive, supportive, or resistive to movement. Immersion depth and percent weight bearing in standing position is as follows: • Waist line (ASIS) = 50% unloaded • Nipple line = 70% unloaded • Seventh cervical vertebra = 90% unloaded Ground reaction forces in water with walking
(slow versus fast) are as follows: • ASIS: 25% unloaded (slow) • Mid trunk: 25-50% unloaded (slow); 25% unloaded fast • Clavicle: 50% unloaded (slow and fast) • Deeper than C7: 75% unloaded (slow and fast) Hydrostatic pressure
waves bend as they pass from one medium (air) to another (water). This bending of light causes objects in water to appear in a different position than they actually are. Refraction affects visual perception and movement in the aquatic environment.
Fluid pressure is exerted equally on all surface areas of an immersed body at rest. Pressure increases with depth according to Pascal’s law. Hydrostatic pressure physiological effects include: • Reduces edema through enhanced venous return • Promotes body detoxification • Reduces training heart rate at a given workload • Increases blood flow to resting muscles but 100- 225% • Improves cardiovascular function through increased central blood volume • Increases work of breathing by 60% at chest depth, providing respiratory training • Enhances proprioceptive awareness through constant pressure feedback The combination of buoyancy and hydrostatic pressure allows for earlier intervention in rehabilitation programs. Relative Density (RD) • Water : 1.0 (this is the baseline reference): ○ Anything <1.0 will float; >1.0 will sink • The human body average: 0.974: ○ Lean body mass: near 1.1 ○ Fat mass: 0.9 ○ Overall body composition (lean versus fatty tissue) will determine how buoyant a person is • Fr esh water density : 28.3 kg/0.03m³ while saltwater density: 29 kg/0.03m³. A body immersed in saltwater will float more easily
Objects in water appear approximately 25% larger and closer to the surface than they actually are. Therapists need to account for refraction when: • Positioning themselves relative to patients • Providing visual cues or feedback • Teaching new movements or exercises • Assessing patient performance Physiological Responses to Immersion Effects of immersion on the cardiovascular and circulatory system are as follows: • Hydrostatic pressure causes compression of veins, translocating blood from the extremities to the thorax • This leads to improved venous return and decreased blood pooling • Cardiac volume increases around 30%, and stroke volume increases by approximately 35% (immersion to the neck) • Heart rate typically decreases by 12-15% in thermoneutral water (92°F) Pulmonary effects include the following: Chest-deep immersion creates unique challenges and benefits for the respiratory system: • Increases work of breathing by 60% • Decreases vital capacity due to hydrostatic pressure • Enhances respiratory muscle strength through resistance training • Improves ventilation-perfusion matching
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